Although litchi can be propagated asexually by various ways the most common and easiest method
adopted all over the world is air-layering. Stooling method of propagation is becoming popular due to
higher success rate as compared to air layering.
Air-layering
Air-layering or 'gootee' is widely accepted method of propagation in India. In this method a healthy andvigorous, upright twig of about one year old and 2.5 to 4 cm in diameter is selected. A circular strip of bark about 2 cm wide just below a bud is completely removed from the selected twig. Care should be
taken to remove all the cambium tissue surrounding the white central wood while removing the bark.
Moist sphagnum moss is packed around this portion and tied with polyethylene sheet, which prevents
the loss of moisture. In about 6 weeks, when the roots are visible through the polythene wrap, the
rooted branch is detached from the parent plant and potted in the nursery. Top of the branch is cut back to maintain a proper ratio of leaves: roots.
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| Figure 1 Materials used for the preparation of the air layer; A- Strip of bark (2 to 3 cm) carefully removed with knife, tree must be well watered before air layer operation for bark loosening; B-C - Debarked ring covered with well-compressed wet sphagnum moss enveloped with clear flexible plastic film; D -Roots formed in the sphagnum moss ball 45 to 60 days after air layering, ready to be removed from the mother plant. |
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| Figure 2 Air layer operation;Air layer operation; A- Raw sphagnum moss collected from sea banks; B- Washed sphagnum moss to remove excess of salt kept in the basket with water for hydration; C - Excess of water removed by hand compression prior to enveloping the ring. |
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Figure 3 Rooting media for air layering.
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Stooling
It involves cutting a 2.5 years old litchi plant in the month of February at 25cm from the ground level.
After a month 6-8 side shoots appear. Except one shoot all the other shoots are selected for stooling in
the month of June. A ring of bark 3cm wide, 20cm from the tip of the shoots is removed. A paste of IBA (25mg) and Lanolin (10g) is applied to the ringed area. Ten days later, soil is mounded around the base of the newly developed shoots so as to cover 10-15 cm of the stem above the ring to encourage adventitious roots. This causes the shoots to root profusely in 2 months. The rooted shoots are separated from the mother plant in the month of September and immediately planted in nursery beds or pots. It is reported that the transplanted shoots have a survival rate of 81-82% as compared with 40%-50% in air-layers.
Wedge Grafting
The wedge graft is fairly easy and heals
rapidly. It works best when the rootstock and scion are of similar diameter preferably
between 0.7 and 1.25 cm. The scion is first prepared by girdling branches of
new growth 21 days prior to grafting. Girdling involves removing a strip of
bark approximately 6 mm in width, situated some 0.5 m from the apex, over the
entire circumference of the branch. Scions are taken only from young trees
which had a period of vigorous growth. Scion material up to 6mm thickness may
be used. The scion must be approximately 10 cm long and contain at least 2-4
buds. It is preferable to use wood from the pervious year rather than young
terminal wood.
A
long, slanting cut is made in the rootstock 30 cm above the ground at a point
where the diameter of the stock is the same as that of the scion. This cut must
not be less than 2.5 cm long, 4mm thick and in stock and somewhat longer if the
stock is wider in diameter. It is nevertheless not recommended to use stock
more than 1 cm thick.
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| Cleft grafting (left) and bark grafting (right) used for litchi propagation. |
Table 1 Grafting compatibility between different litchi root stock and scion cultivars.
Managing Nursery
Stocks
Fertilizers can be applied once the young
plants begin to produce new growth. Fertilizer application is to be done very
carefully. Vigorous growth of plant is always attractive to the buyer. Heavy
manuring is not beneficial for storage of plants. Light manuring, watering is
also important. Watering is done according to need of the plant. The nursery
should have a water source of its own. Digging a well (12 m deep x 3 m
diameter) and installation of a 2.0 HP pump set with accessories are considered
appropriate. Sprinkler system of irrigation is not advisable at the beginning.
For
sufficient vegetative and reproductive growth of plants, good drainage system
must be developed in between the beds and around the nursery. Adequately gentle
slope in the pot bed surface is also desirable. It is extremely important to
ensure that water logging does not occur in and around the pots and beds. Keen
observation on attack of different pests and diseases is required. If the
mother plants are infected, the propagated plants will also be infected
therefore, necessary control measures in mother plants as well as in nursery
plants should be taken immediately on observation.